A new path: Tightest tolerances for large SBQ diameter

A project, with its focus on establishing DAYE as the most competitive future-oriented special steel company in the field of SBQ production, can only be realized with a reliable and experienced partner close at hand.


Daye Special Steel Co., Ltd belongs to the Chinese CITIC Pacific Steel Group and is based in Huangshi, in southeast Hubei province. Daye is one of the largest and most successful special steel producers in China and provides products, both nationally and internationally, for a wide variety of industries, including the automobile, maritime, aerospace and energy industries.


With the integration of the latest KOCKS RSB® in their ultra-modern 900,000 t/a medium bar mill, Daye showed they were prepared to tread a totally new path in their provision of tightest tolerances for larger SBQ diameters (round bar within the range of 50.0 mm diameter to 130.0 mm diameter in straight lengths) to an increasingly demanding downstream industry. In the aerospace, new energy, defense, automotive, railway and engineering industries, technological advances mean that demand is growing for special bar quality steel with closer tolerances even in the larger dimensional ranges.

A project of ambition and reach, with its focus on establishing Daye Special Steel Co., Ltd as the most competitive future-oriented special steel company in the field of SBQ production, can only be realized with a reliable and experienced partner close at hand. The decision in July 2014 to award KOCKS the contract for supply of their biggest sizing block, the RSB® 500++/4, was highly influenced by the excellent performance, the reliability and the trouble-free operation of the RSB®, in use since the beginning of the last decade in Daye’s existing specialty bar mill.


The new heavy duty Reducing & Sizing Block is equipped with four stand positions and its sturdy design allows the entire size range to be finished at low temperatures, granting lowest possible operating costs by either minimizing or avoiding post-processing heat treatments, all while maintaining closest tolerances. The Reducing & Sizing Block allows the rolling of the complete finished size range out of only one pass series from the 16-stand 2-high roughing and intermediate mill; this significantly increases the productivity of the mill by reducing the number of required RSB® entry feeders down to only five. A special feature of this 500 mm heavy-duty RSB® is that every roll has its own drive, giving this sizing unit a compact design and a small footprint (Z-Drive design). Following a problem-free commissioning period, the first bar was rolled with the RSB® in January 2016 to the fullest satisfaction of Daye.

Experience adds value
  • This project is further proof that KOCKS’ reputation for reliability – delivery on time, on target and on budget – extends even to new systems such as the RSB® 500++, delivering the best results right from the 1st day after commissioning. The execution and design of such an innovative project can only be reliably implemented when backed up with years of experience with 3-roll technology. The knowledge of deformation and spread behavior of the different material grades in 3-roll stands was again crucial for the dimensioning and design of such an innovative new rolling mill.
  • The RSB® can produce any desired finished dimension of the complete size range in any desired sequence either by remote-controlled roll gap adjustment within a billet gap or by quick stand changing within less than five minutes, thus still further improving the down-times and the availability of this future-oriented rolling mill.
Innovation Inside

This project offers:

  • the first 3-roll finishing block worldwide that produces diameters of up to 160mm with a tolerance precision of up to 1/12 DIN; also delivers best conditions for downstream processes thanks to improved surface quality.
  • a completely new block design with a modular roll drive concept allows for a much smaller block footprint despite extremely high allowable rolling forces and rolling torque of the stands, and reduces customer’s level of investment.